FORTY YEARS AGO, the first two computers on the Arpanet, the military network that was the precursor to the internet, exchanged login information. One of them crashed, incidentally, which must be some consolation to users of Microsoft operating systems; it shows the "Blue Screen of Death" that used to plague them has a venerable provenance.

Twenty years ago, a young British physicist named Tim Berners-Lee working in Cern embarked on a project that would make him Gutenberg's successor. It was the world wide web. Ten years later teenager Shawn Fanning retreated to his bedroom and wrote software for sharing music files across the net. In the process, he also signed the death warrant of the old-style record industry.

But this month also sees another significant anniversary which has received less attention. For Blogger, the web service that enabled anyone who could type to publish online, is 10 years old this month. On 1 September, there was a party in San Francisco to mark the moment, attended by – among others – Blogger's founder, Evan Williams (who later founded Twitter), and the journalist Scott Rosenberg, who has just published "Say Everything" (sayeverything.com), an absorbing book on the phenomenon that Blogger enabled.

For mainstream journalism, with its newt-like attention span, blogging is yesterday's news. Twitter is currently the focus of media ridicule, but next month the circus will have moved on to something else. So it's worth pondering the numbers mentioned at the San Francisco bash. Blogger (now owned by Google) has 10 million "active" users, or people who have posted something new over the past 30 days. The number of "seven-day active" users has doubled over the past two years. Blogger has 300m unique visits a month. In an average minute, 270,000 words are written on its blogs, and something like a quarter of a trillion words have been written on Blogger since its foundation.

And that's just on Blogger. Other services like Wordpress, LiveJournal and Typepad can produce equally striking statistics. Mainstream media may have lost interest in blogging, but that just confirms the extent to which it has become an accepted part of life in the networked world. Of course, there was blogging before Blogger. In fact, as Mr Rosenberg points out, the quest to identify the first blogger is futile because there were "web logs" from the beginning of the web. But back then you had to be technically adept to publish on the web. The significance of Blogger was that it enabled just about anyone to publish online. You just signed up, started writing, pressed a button and – Hey Presto! – you were a blogger. And it was free (it still is).

"When a true genius appears in the world," wrote Jonathan Swift, "you may know him by this sign, that the dunces are all in confederacy against him." So it was with blogging. It was ridiculed as self-indulgent, lazy vanity publishing; lampooned as the product of obsessives tapping feverishly in their pyjamas; blasted as a parasitic activity, feeding on the blood of hard-working professional journalists; and derided as a doomed fad because there was no "business model" to support it. After all, virtually no one makes money from his or her blog, so the thing clearly didn't have a future.

And guess what? Blogging is thriving. In virtually every area of human interest, the diversity and quantity of fact and opinion available online dwarfs what was available in the print era. In the old days the News of the Worldhad a ludicrous slogan: "All Human Life Is Here", a promise on which no publication could ever hope to deliver. The "blogosphere", as it's come to be called, is the first medium we've ever had which could conceivably live up to the slogan.

The long-term significance of Blogging is that it reverses a trend that had become increasingly worrying in an era dominated by mass media, namely the erosion of what the cultural critic Jurgen Habermas called "the public sphere" – an area where citizens gather to generate opinions and attitudes that affirm or challenge the actions of the state. Mass media offered the illusion of diversity while narrowing the range of real choices available – the "600 channels and nothing on" syndrome. Blogging has revived – and begun to expand – the public sphere, and in the process may revitalise our democracies. If it does, then we will have Evan Williams largely to thank for it.